If the sun burned out, Earth would go dark in about 8 minutes and 20 seconds, the time it takes light to travel the 150 million kilometers between us. After that, temperatures would plummet, plants would die, and the planet would eventually become a frozen rock hurtling through space. But the full picture is more interesting than simple extinction. The timeline stretches from minutes to millennia, and not every living thing would disappear.
The First 8 Minutes
Light travels at 300,000 kilometers per second, and the sun sits roughly 150 million kilometers away. That means you’d have about 8 minutes and 20 seconds of perfectly normal daylight after the sun stopped shining. You wouldn’t feel colder. The sky would look the same. Nothing about your immediate experience would hint that anything had changed.
Then, without warning, the sky would go black. Not sunset-black, but a total darkness broken only by stars. The moon would vanish too, since moonlight is just reflected sunlight. Every planet visible in the night sky would blink out one by one as the last of the sun’s light passed them by.
Gravity travels at the speed of light as well. So for those same 8 minutes, Earth would continue orbiting as if nothing happened. Once the gravitational influence disappeared, the planet would fly off in a straight line at its current orbital speed of about 30 kilometers per second, drifting into interstellar space with no star to circle.
The First Week: A Fast Freeze
The temperature drop would be shockingly fast. Within a week, the average global surface temperature would fall below 0°F (roughly minus 18°C). That’s a worldwide average, meaning some places would be far colder. Coastal regions near the ocean would hold warmth slightly longer because water releases stored heat more slowly than land, but even oceans would begin forming surface ice within weeks.
The atmosphere itself would act as a temporary blanket. Earth’s thick layer of air traps residual heat the same way it traps solar warmth today, slowing the cooling process compared to an airless body like the moon. But “slowing” is relative. Most outdoor environments would become uninhabitable for humans within days without shelter and heating.
The First Year: Deep Cold Sets In
After one year, average surface temperatures would drop to around minus 100°F (minus 73°C). That’s colder than anywhere naturally recorded on Earth and comparable to winter conditions on Mars. The oceans would freeze over on the surface, though a thick layer of ice actually insulates the water beneath it. Deep ocean water would remain liquid for a surprisingly long time, potentially thousands of years, kept warm by Earth’s own internal heat and the insulating ice cap above.
Rain and weather patterns would stop almost entirely. Without solar heating to drive evaporation and atmospheric circulation, the water cycle would grind to a halt. The atmosphere itself would eventually begin to change. Nitrogen and oxygen wouldn’t freeze at these temperatures (they require far more extreme cold), but carbon dioxide would start freezing out of the air at around minus 109°F, falling as dry ice snow.
What Happens to Plants and Oxygen
Photosynthesis would cease immediately without sunlight, and most plants would die within days to weeks depending on their stored energy reserves. Large trees could actually hold on for several years, possibly even a few decades, because they store significant energy in their trunks and root systems and metabolize slowly. But they’d eventually starve without light to power new growth.
The loss of photosynthesis means no new oxygen production. However, the atmosphere currently holds enough oxygen to last thousands of years even without replenishment. Oxygen wouldn’t be the immediate crisis. Cold, darkness, and the collapse of food chains would kill most life long before oxygen became scarce. With plants gone, herbivores starve. With herbivores gone, predators follow. The entire land-based food web would unravel within months.
Life That Would Survive
Not everything depends on the sun. Deep on the ocean floor, hydrothermal vents blast superheated, chemical-rich water into the surrounding sea. Entire ecosystems thrive there right now, powered not by sunlight but by a process called chemosynthesis, where microorganisms convert volcanic chemicals into energy. These communities include tube worms, shrimp, crabs, and fish, none of which have ever relied on solar energy. As long as Earth’s core stays hot and tectonic activity continues, these ecosystems would carry on largely unaffected.
NASA’s astrobiology research has highlighted hydrothermal vents as proof that life can thrive completely independent of the sun. The chemicals pouring from these vents would be toxic to humans, but the microorganisms at the base of these food chains convert them into usable energy. This discovery is part of why scientists consider icy moons like Europa, which has a subsurface ocean and likely hydrothermal activity, as candidates for extraterrestrial life.
Certain bacteria deep underground would also persist. Microbes living kilometers below the surface in rock formations generate energy from chemical reactions with minerals. They operate on geological timescales and would barely notice the sun’s absence.
Could Humans Survive?
In theory, small groups of humans could survive for an extended period, but it would require immediate, coordinated action and access to the right infrastructure. The key resource is geothermal energy. Earth’s core burns at over 5,000°C, as hot as the surface of the sun, and that heat is continuously replenished by the decay of radioactive elements deep underground. This “natural nuclear” energy would remain available for billions of years.
Communities near geothermal hotspots (Iceland, parts of New Zealand, the western United States, Japan) would have the best shot. Geothermal energy can generate electricity, heat enclosed spaces, and even warm greenhouses for food production. Underground aquifers in some regions hold water at 60°C or higher, accessible with existing drilling technology. Nuclear power plants, where they remained operational, could also provide electricity and heat for sealed habitats.
The challenge goes beyond energy. You’d need enclosed, insulated environments to grow food under artificial light, recycled water systems, and enough initial supplies to bridge the gap while these systems scaled up. The surface would eventually become so cold that venturing outside would require something closer to a spacesuit than a winter coat. Humanity’s survival would look less like life on Earth and more like a permanent space station, just built underground.
What Happens to the Rest of the Solar System
Earth wouldn’t be the only planet affected, but the impact would vary. Mars and the other rocky planets, which depend almost entirely on absorbed sunlight for their surface temperatures, would freeze quickly. Mars is already cold; without the sun, it would become indistinguishable from deep space within months.
The gas giants tell a different story. Jupiter and Saturn both radiate significantly more energy than they absorb from the sun, powered by internal heat left over from their formation and ongoing gravitational compression. Jupiter, in particular, has a substantial energy imbalance: its internal heat source is a major driver of its atmospheric dynamics. These planets would cool over time, but far more slowly than the rocky worlds. Their moons with subsurface oceans, like Europa and Enceladus, might remain habitable for microbial life for billions of years, sustained by tidal heating from their parent planets rather than sunlight.
Without the sun’s gravity anchoring the solar system, every planet would drift apart on its own trajectory through the Milky Way. Within a few centuries, what was once a solar system would be scattered objects flying independently through interstellar space, each carrying whatever warmth they had left.